EXPERIMENTAL AND NUMERICAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT WITH TWISTED TAPE INSERT

Embedding twisted tape (TT) inserts are a well-known technique widely used in industry because of their easiness in manufacturing and installation. The current work investigates the distribution of local wall temperature and Nusselt number with twisted tape inserts using an infrared camera. The thermohydraulic performance of the twisted tape is evaluated for various geometrical parameters. A numerical and experimental analysis is performed for twist ratios of 2.5, 3.5, 5, and 10 with varying tape widths of 10, 14, 16, and 18 mm. The analysis is carried out for a Reynolds number ranging from 7500 to 30,000. The results obtained indicate an increase in the Nusselt number (Nu) and friction factor (<i>f</i>) with the increment in tape width and decrement in the tape pitch. The maximum rise in Nu and <i>f</i> is observed to be 1.72 and 2.19 times in the plain tube for full width and minimum twist ratio. Empirical correlations, incorporating geometrical parameters of TT, such as twist ratio and normalized width (<i>W/d</i>), are developed for Nu and <i>f</i> for an internal flow inside a circular tube with twisted tape inserts, using water as working fluid. The correlations predict all the data for f and Nu with a mean absolute deviation of 5.47 and 7.18&#37;, respectively.